The Acústica research group at the UPV/EHU's Faculty of Engineering in Bilbao has used the scientific advances existing in the field of acoustics, and musical acoustics in particular, as well as the latest technological advances in tools to record and analyse the data obtained, in an acoustic study of wind instruments in Basque folklore. The research work is reflected in the PhD thesis of the researcher Asier Agos-Esparza, entitled Función acústica del txistu y su familia instrumental (Acoustic function of the txistu and its family of instruments) and was conducted in collaboration with the Juan Crisóstomo de Arriaga Conservatoire of Music of Bilbao.

The main aim of this study was to characterise the txistu and the instruments in its family so as to "provide a scientific explanation of how the sound is generated and propagated," explained the researcher, "and also to see which parameters influence its acoustics and how they do this, and to try to adjust these parameters to optimise the acoustics of the txistu".

The methodology adopted consisted of studying the properties of txistus and the instruments in its family using a specific geometry. After that, these properties were varied in a controlled way and their impact on the final sound of the instrument was studied. When the change in the variables studied entailed an irreversible modification of the instrument, such as varying the diameter of the pipe, new txistus were made incorporating the features the researchers wanted to study.

It was a multidisciplinary piece of work in which the problem was tackled from a range of points of view. "We applied the theoretical knowledge on how the standing waves are produced in the pipe when the air inserted by the player interacts with the air present inside the pipe," explained Agos. "We studied the process to build the instrument and we created various txistus with different characteristics. We analysed all these instruments with the help of musicians and also by using a blowing machine to eliminate the human factor." They also produced some software to calculate the physical and psychoacoustic properties of the music produced by these instruments.

Modifying the interior geometry of the pipe

The researchers set out to produce a better-tuned txistu by modifying the inside of the pipe. As Agos explained, "when we play a traditional cylindrical txistu by opening or closing its holes completely, the pitch we obtain is quite different from that of a piano". To improve the pitch, txistu players correct the notes by slightly opening or closing one or more of the holes in the instrument. "Yet," he added, "by modifying the pipe it is possible to produce an instrument whose pitch is closer to that of a piano by using positions in which the holes remain fully open or closed."

The researchers gathered, analysed and compared the data produced by a traditional txistu and by the new prototype. The shape of the internal pipe of the new txistu prototype is not a pure cylinder like that of the traditional txistu. What is more, the location, size and height of the holes have been changed. The analysis of all this reveals considerable pitch differences between the two txistus

In the researcher's view, "this study will help makers predict the characteristics of the instrument more accurately".  Likewise, "it will help to transfer the changes called for by instrumentalists into specific changes in the process to make them," he concluded, "by consistently moving towards an instrument with the acoustic characteristics that players and the public regard as attractive".

Additional information

Asier Agos-Esparza (Iruñea-Pamplona, 1979), a graduate in Physics and an Electronics Engineer, produced his PhD thesis entitled Función acústica del txistu y su familia instrumental  (Acoustic function of the txistu and its family of instruments) under the supervision of María Jesus Elejalde and Erica Macho, in the Acústica research group of the UPV/EHU's department of Applied Physics I of the Faculty of Engineering in Bilbao. The study was made in collaboration with Aitor Amilibia and Iñaki Imatz of the Juan Crisóstomo de Arriaga Conservatoire of Music in Bilbao, who have been working for a long time on the geometry of the pipe of the txistu.

Photos: Asier Agos. UPV/EHU (Home: Danel Solabarrieta. Elhuyar Fundazioa)